Chemical mechanical polishing pad

ABSTRACT

The present invention provides methods of CMP polishing a metal surface, such as a copper or tungsten containing metal surface in a semiconductor wafer, the methods comprising CMP polishing the substrate with a CMP polishing pad that has a top polishing surface in a polishing layer which is the reaction product of an isocyanate terminated urethane prepolymer and a curative component comprising a polyol curative having a number average molecular weight of 6000 to 15,000, and having an average of 5 to 7 hydroxyl groups per molecule and a polyfunctional aromatic amine curative, wherein the polishing layer would if unfilled have a water uptake of 4 to 8 wt. % after one week of soaking in deionized (DI) water at room temperature. The methods form coplanar metal and dielectric or oxide layer surfaces with low defectivity and a minimized degree of dishing.

The present invention relates to methods comprising chemical mechanicalpolishing (CMP polishing) to planarize a metal surface in asemiconductor wafer, magnetic or optical substrate and thereby formingcoplanar metal and dielectric layer surfaces with low defectivity and aminimized degree of dishing, as well as to CMP polishing pads used inthe methods. More particularly, the present invention relates to methodswherein CMP polishing comprising polishing the semiconductor wafer,memory or optical substrate with a CMP polishing pad comprising thepolyurethane a reaction product of an isocyanate terminated urethaneprepolymer and a curative component comprising from 60.3 to 70 wt. %, ofa polyol curative, having a number average molecular weight of 6000 to15,000 and an average of 5 to 7 hydroxyl groups per molecule.

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited onto and removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting and dielectric materials maybe deposited using a number of deposition techniques, e.g. physicalvapor deposition (PVD), also known as sputtering, chemical vapordeposition (CVD), plasma-enhanced chemical vapor deposition (PECVD) andelectrochemical plating. As layers of materials are sequentiallydeposited and removed, the uppermost surface of the wafer becomesnon-planar and must be planarized to enable effective deposition ofsubsequent layers on the wafer. Accordingly, each deposited layer isplanarized by chemical mechanical planarization, or chemical mechanicalpolishing (CMP polishing). Thus, CMP polishing is useful for removingundesired surface topography and surface defects, such as roughsurfaces, agglomerated materials, crystal lattice damage, scratches andcontaminated layers or materials.

Metal layers are deposited on the semiconductor wafer to form conductivepathways as metal contacts and interconnects for multilevelmetallization of semiconductor integrated circuits. Metals may bedeposited as layers, such as to fill trenches or troughs, fill postholes, or to include micro- or nano-scale conductive circuitry; andmetals may be deposited in larger features of the semiconductor, such asbuses and bond pads. However, in the CMP polishing of softer or moreductile metals, such as copper, the metals can be removed in anon-planar fashion, such as dishing. The term “dishing” refers to aphenomenon wherein CMP polishing results in a metal recess in a lowarea, such as an oxide cavity or trough, where the metal layer should,but does not remain planar or coplanar with lower layers of thesubstrate wafer after CMP polishing.

The dishing problem has become more prominent in recent years assemiconductor wafers and devices are becoming increasingly complex, withfiner features and more metallization layers. This trend requiresimproved performance from polishing consumables (pads and slurries) tomaintain planarity and limit polishing defects. Defects in such wafersand devices can create electrical breaks or shorts in the conductinglines that would render the semiconductor device inoperative. It isgenerally known that one approach to reduce polishing defects, such asmicro-scratches or chatter marks, is to use a softer polishing pad.Further, CMP polishing of soft metal layers may necessitate the use ofsofter CMP polishing pads. However, while CMP polishing with a soft padcan improve defectivity in substrates polished using such pads, suchsoft pads can increase dishing in metallized semiconductor wafersurfaces due to the flexible nature of the soft pad.

U.S. patent publication no. US2015/0306731 A1, to Qian et al., disclosesCMP polishing pads which are the reaction product of a polyisocyanateprepolymer and a curative containing less than 60 wt. % of a highmolecular weight polyol curative having an average of 3 to 10 hydroxylgroups and more than 40% of a difunctional curative selected from diolsand diamines. Qian et al. fails to disclose methods of CMP polishingductile metals and softer substrates. Further, Qian fails to discloseany CMP polishing pad that provides a solution to the problem of dishingin metallized semiconductor wafer surfaces. Accordingly, there remains aneed for a metal CMP polishing pad and metal CMP polishing method thatenables reduced defectivity and improved dishing performance.

The present inventors have sought to solve the problem of enabling theCMP polishing of metal surfaces in semiconductor wafer or devicesubstrates to provide reduced defectivity and, at the same time, reduceddishing of the metal on the substrate surface.

STATEMENT OF THE INVENTION

In accordance with the present invention, methods of CMP polishing ametal surface in a semiconductor wafer, magnetic or optical substratecomprise CMP polishing the substrate with a CMP polishing pad that has atop polishing surface in a polishing layer, the polishing layercomprising: a reaction product of an isocyanate terminated urethaneprepolymer having 8.5 to 9.5 wt. % or, preferably, from 8.95 to 9.25 wt.% of unreacted NCO groups; and a curative component comprising from 60.3to 70 wt. %, or, preferably, 60.5 to 67 wt. %, or, more preferably, 60.6to 65 wt. %, based on the solids weight of the curative component, of apolyol curative, having a number average molecular weight of 6000 to15,000, or, preferably, from 10,000 to 13,000, and having an average of5 to 7 or, preferably, 6 hydroxyl groups per molecule; and from 30 to39.7 wt. %, preferably, 33 to 39.5 wt. % or, more preferably, 35 to 39.4wt. %, based on the solids weight of the curative component, of apolyfunctional aromatic amine curative, such as a difunctional curative,preferably, 4,4′ methylene bis (2 chloroaniline) (MBOCA), 4,4′ methylenebis (3 chloro 2,6 diethylaniline) (MCDEA), diethyltoluenediamine(DETDA); 3,5 dimethylthio 2,4 toluenediamine (DMTDA), isomers thereof,or mixtures thereof, wherein the polishing layer would if unfilled orlacking in added porosity have a water uptake of 4 to 8 wt. % after oneweek of soaking in deionized (DI) water at room temperature and a ShoreD hardness ranging of from 28 to 64, or, preferably, from 30 to 60 or,more preferably, from 35 to 55, the top polishing surface adapted toplanarize and polish the metal surface in the substrate and therebyforming coplanar metal and dielectric or oxide layer surfaces with lowdefectivity and a minimized degree of dishing.

In accordance with the methods of the present invention, the methodscomprise CMP polishing a substrate with a polishing layer wherein thepolishing layer comprises a reaction product wherein the stoichiometricratio of the reactive hydrogen groups (defined as the sum of NH₂ and OHgroups) in the curative component to the unreacted NCO groups in theisocyanate terminated urethane prepolymer ranges from 0.85:1 to 1.15:1,or, preferably from 1.02:1 to 1.08:1.

In accordance with the methods of the present invention, the methodscomprise CMP polishing a copper or tungsten containing metal surface ina semiconductor wafer, preferably, a copper containing surface, such asa bulk copper surface, a copper barrier surface.

In accordance with the methods of the present invention, the methodscomprise CMP polishing with a CMP polishing pad having a polishing layerthat consists essentially of the reaction product of a curativecomponent that has 5 wt. % or less or that is substantially free of anydiol, such as polytetramethylene glycol (PTMEG), poly(propylene glycol)PPG, 1,4-butane diol, ethylene glycol, diethylene glycol, or theirmixtures. The term “substantially free of any diol” means that thecurative component comprises 2,000 ppm or less or, preferably, 1,000 ppmor less of any diol.

In accordance with the methods of the present invention, the methodscomprise CMP polishing a substrate with a CMP polishing pad having apolishing layer that has a specific gravity (SG) of from 0.4 to 1.15 or,preferably, from 0.6 to 1.1 or, more preferably, from 0.7 to 1.0. Inaccordance with these methods, the methods comprise CMP polishing with aCMP polishing pad that comprises a polishing layer wherein the reactionproduct which, when unfilled or lacking in added porosity, would have anSG of from 1.0 to 1.3 or, preferably, from 1.1 to 1.2.

In accordance with the methods of the present invention, the methodscomprise CMP polishing with a CMP polishing pad having a polishing layerthat comprises gas filled or hollow microelements, such as, preferably,polymeric microspheres from which the CMP polishing derives itsporosity. Preferably, the amount of such gas filled or hollowmicroelements ranges from 0 to 5 wt. %, or, preferably, from 1.5 to 3wt. %, based on the solids weight of the polishing layer.

In accordance with the methods of the present invention, the CMPpolishing comprises: providing a CMP polishing apparatus having aplaten; providing at least one substrate to be polished; providing a CMPpolishing pad of the present invention; installing onto the platen theCMP polishing pad; optionally, providing a polishing medium at aninterface between a polishing surface of the CMP polishing pad and thesubstrate, preferably, wherein the polishing medium is selected from thegroup consisting of a polishing slurry and a non-abrasive containingreactive liquid formulation; and, creating dynamic contact between thepolishing surface and the substrate, wherein at least some material isremoved from the substrate.

In accordance with the methods of the present invention, the methodscomprise CMP polishing with the CMP polishing pad of the presentinvention and, further comprise: providing a polishing medium at aninterface between the polishing surface and the substrate; and, creatingdynamic contact between the polishing surface and the substrate, such asby rotating the substrate, rotating the CMP polishing pad having thepolishing layer, or rotating both, wherein at least some material isremoved from the substrate.

In accordance with the methods of the present invention, the methodscomprise: CMP polishing with the CMP polishing pad of the presentinvention and, separately or at the same time, conditioning thepolishing layer of the CMP polishing pad with a conditioning disk sothat the CMP polishing pad has a surface microtexture.

In another aspect of the present invention, CMP polishing pads comprisea polishing layer which is a reaction product of an isocyanateterminated urethane prepolymer having 8.5 to 9.5 wt. % unreacted NCOgroups; and a curative component comprising from 60.3 to 70 wt. %, or,preferably, 60.5 to 67 wt. %, or, more preferably, 60.6 to 65 wt. %,based on the solids weight of the curative component, of a polyolcurative, having a number average molecular weight of 6000 to 15,000,or, preferably, from 10,000 to 13,000, and an average of 5 to 7 or,preferably, 6 hydroxyl groups per molecule; and 30 to 39.7 wt. %,preferably, 33 to 39.5 wt. %, or, more preferably, 35 to 39.4 wt. %,based on the solids weight of the curative component, of apolyfunctional aromatic amine curative, such as a difunctional curative,preferably, 4,4′ methylene bis (2 chloroaniline) (MBOCA), 4,4′ methylenebis (3 chloro 2,6 diethylaniline) (MCDEA), diethyltoluenediamine(DETDA); 3,5 dimethylthio 2,4 toluenediamine (DMTDA), isomers thereof,or mixtures thereof, wherein the polishing layer would if unfilled orlacking in added porosity have a water uptake of 4 to 8 wt. % after oneweek of soaking in deionized (DI) water at room temperature and a ShoreD hardness as measured according to ASTM D2240-15 (2015) ranging of from28 to 64, or, preferably, from 30 to 60 or, more preferably, from 35 to55, the top polishing surface adapted to planarize and polish the metalsurface in the substrate and thereby forming coplanar metal anddielectric or oxide layer surfaces with low defectivity and a minimizeddegree of dishing.

In accordance with the CMP polishing pads of the present invention, theCMP polishing pad has a polishing layer that consists essentially of thereaction product of a curative component that has 5 wt. % or less orthat is substantially free of any diol, such as polytetramethyleneglycol (PTMEG), poly(propylene glycol) PPG, 1,4-butane diol, ethyleneglycol, diethylene glycol, or their mixtures. The term “substantiallyfree of any diol” means that the curative component comprises 2,000 ppmor less or, preferably, 1,000 ppm or less of any diol.

In accordance with the CMP polishing pads of the present invention, thepolishing layer comprises a reaction product wherein the stoichiometricratio of the reactive hydrogen groups (defined as the sum of NH₂ and OHgroups) in the curative component to the unreacted NCO groups in theisocyanate terminated urethane prepolymer ranges from 0.85:1 to 1.15:1,or preferably from 1.02:1 to 1.08:1.

In accordance with CMP polishing pads of the present invention, the CMPpolishing pads have a polishing layer that has a specific gravity (SG)of from 0.4 to 1.15 or, preferably, from 0.6 to 1.1 or, more preferably,from 0.7 to 1.0.

In accordance with the CMP polishing pads of the present invention, thepolishing layer is a reaction product which, when unfilled or lacking inadded porosity, would have an SG of from 1.0 to 1.3 or, preferably, from1.1 to 1.2.

In accordance with the CMP polishing pads of the present invention, thepolishing layer comprises gas filled or hollow microelements, such as,preferably, polymeric microspheres from which the CMP polishing derivesits porosity. Preferably, the amount of such gas filled or hollowmicroelements ranges from 0 to 5 wt. %, or, more preferably, from 1.5 to3 wt. %, based on the solids weight of the polishing layer.

Unless otherwise indicated, conditions of temperature and pressure areambient temperature and standard pressure. All ranges recited areinclusive and combinable.

Unless otherwise indicated, any term containing parentheses refers,alternatively, to the whole term as if no parentheses were present andthe term without them, and combinations of each alternative. Thus, theterm “(poly)isocyanate” refers to isocyanate, polyisocyanate, ormixtures thereof.

All ranges are inclusive and combinable. For example, the term “a rangeof 50 to 3000 cPs, or 100 or more cPs” would include each of 50 to 100cPs, 50 to 3000 cPs and 100 to 3000 cPs.

As used herein, the term “ASTM” refers to publications of ASTMInternational, West Conshohocken, Pa.

As used herein, the term “lacking in added porosity” means that a CMPpolishing pad of polishing layer thereof contains no gas filled orhollow microspheres or pores formed from addition of gas other thanambient air, such as nitrogen gas (N₂) or CO₂ or air under a pressure ofgreater than 1 atmosphere (101 kPa), to the reaction mixture.

As used herein, the term “number average molecular weight” of a polyolmeans the weight as determined by the product of its hydroxyl equivalentweight and the average number of hydroxyl groups per molecule. Thehydroxyl equivalent weight is calculated from hydroxyl number, in mgKOH/g, as reported in a given manufacturer's specification or asdetermined by titration of the polyol according to ASTM D4274 (2011),using the following formula:

Hydroxyl equivalent weight=56100/hydroxyl number

As used herein, the term “polyisocyanate” means any isocyanate groupcontaining molecule having three or more isocyanate groups, includingblocked isocyanate groups.

As used herein, the term “polishing medium” as used herein and in theappended claims encompasses particle containing polishing solutions andnon-particle containing polishing solutions, such as abrasive free andreactive liquid polishing solutions.

As used herein, the term “polyisocyanate prepolymer” means anyisocyanate group containing molecule that is the reaction product of anexcess of a diisocyanate or polyisocyanate with an active hydrogencontaining compound containing two or more active hydrogen groups, suchas diamines, diols, triols, and polyols.

As used herein, the term “Shore D hardness” is the hardness of a givenmaterial as measured according to ASTM D2240-15 (2015), “Standard TestMethod for Rubber Property—Durometer Hardness”. Hardness was measured ona Rex Hybrid hardness tester (Rex Gauge Company, Inc., Buffalo Grove,Ill.), equipped with a D probe. Six samples were stacked and shuffledfor each hardness measurement.

As used herein, the term “specific gravity” or SG refers to the relativedensity of a given material to the density of water, as determined byweighing a known volume of the given material and dividing the result bythe weight of the same volume of water, as measured according to ASTMD1622 (2014).

As used herein, unless otherwise indicated, the term “viscosity” refersto the viscosity of a given material in neat form (100%) at a giventemperature as measured using a rheometer, set at an oscillatory shearrate sweep from 0.1-100 rad/sec in a 50 mm parallel plate geometry witha 100 μm gap.

As used herein, unless otherwise indicated, the term “wt. % NCO” refersto the amount as reported on a spec sheet or MSDS for a given NCO groupor blocked NCO group containing product.

As used herein, the term “wt. %” stands for weight percent.

The present invention provides CMP polishing methods and chemicalmechanical polishing pads that reduced defectivity and dishing inplanarizing a metal surface, such as a copper metal surface in asemiconductor wafer. The chemical mechanical polishing pad of thepresent invention has a polishing layer that exhibits both a desirablebalance of physical properties that correlates well with low defectpolishing performance and conditionability to facilitate the formationof microtexture using a diamond conditioning disk, while maintaining ahigh polishing rate. Accordingly, the balance of properties enabled bythe polishing layer of the present invention provides the ability to,for example, polish semiconductor wafers at an efficient rate withoutdamaging the wafer surface by creating micro-scratch defects that couldcompromise the electrical integrity of the semiconductor device. It wassurprising to find in CMP polishing a substrate containing a metal ormetallized surface, the CMP polishing pad having a polishing layer ofthe present invention can improve defectivity and at the same timeprovide comparable or better dishing performance in planarizing orpolishing a metal surface.

The CMP polishing pads of the present invention have a polishing layerwherein the water uptake of the unfilled polishing layer or polishinglayer lacking in added porosity ranges from 4 to 8 wt. % after one weekof soaking in deionized (DI) water at room temperature. The presentinventors have found that such an unusually high water uptake enablesdefect free CMP polishing of metal or metallized substrates inaccordance with the present invention with reduced dishing in thesubstrates. Further, the CMP polishing pads have a polishing layer thatenable the methods of the present invention to succeed while usingconventional CMP polishing methods.

The methods of the present invention for CMP polishing of a substratepreferably comprises: providing a chemical mechanical polishingapparatus having a platen; providing at least one substrate to bepolished; providing a chemical mechanical polishing pad of the presentinvention; installing onto the platen the chemical mechanical polishingpad; optionally, providing a polishing medium at an interface between apolishing surface of the chemical mechanical polishing pad and thesubstrate (preferably, wherein the polishing medium is selected from thegroup consisting of a polishing slurry and a non-abrasive containingreactive liquid formulation); creating dynamic contact between thepolishing surface and the substrate, wherein at least some material isremoved from the substrate; and, optionally, conditioning of thepolishing surface with an abrasive conditioner. Preferably, in themethod of the present invention, the chemical mechanical polishingapparatus provided further includes a light source and a photosensor(preferably a multisensor spectrograph); and, the chemical mechanicalpolishing pad provided further includes an endpoint detection window;and, the method further comprises: determining a polishing endpoint bytransmitting light from the light source through the endpoint detectionwindow and analyzing the light reflected off the surface of thesubstrate back through the endpoint detection window incident upon thephotosensor.

The present invention provides methods of polishing a substrate,comprising: providing a chemical mechanical polishing apparatus having aplaten; providing at least one substrate having a metal or metallizedsurface, such as one containing copper or tungsten; providing a chemicalmechanical polishing pad according to the present invention; installingonto the platen the chemical mechanical polishing pad; optionally,providing a polishing medium at an interface between the polishingsurface and the substrate; creating dynamic contact between thepolishing surface and the substrate, wherein at least some material isremoved from the substrate.

In accordance with the methods of the present invention for polishing asubstrate, the at least one substrate is selected from the groupconsisting of at least one of a magnetic substrate, an optical substrateand a semiconductor substrate.

The CMP polishing methods of the present invention may be carried out ina conventional manner to create dynamic contact between the polishingsurface of the polishing layer and the substrate, wherein a wafercarrier, or polishing head, is mounted on a carrier assembly. Thepolishing head holds the wafer and positions the wafer in contact with apolishing layer of a polishing pad that is mounted on a table or platenwithin a CMP apparatus. The carrier assembly provides a controllablepressure between the wafer and polishing pad. Simultaneously, apolishing medium (e.g., slurry) is dispensed onto the polishing pad andis drawn into the gap between the wafer and polishing layer. Inpolishing, the polishing pad and wafer typically rotate relative to oneanother. As the polishing pad rotates beneath the wafer, the wafersweeps out a typically annular polishing track, or polishing region,wherein the wafer's surface directly confronts the polishing layer. Thewafer surface is polished and made planar by chemical and mechanicalaction of the polishing layer and polishing medium on the surface.

The present invention provides a CMP polishing pad, comprising: apolishing layer having a polishing surface, wherein the polishingsurface is adapted for polishing a substrate selected from the groupconsisting of at least one of a magnetic substrate, an optical substrateand a semiconductor substrate. The polishing layer thus comprises both asurface macrotexture, such as one or more grooves, and a surfacemicrotexture.

The polishing surface of the polishing layer of the chemical mechanicalpolishing pad of the present invention is adapted for polishing asubstrate having a metal or metallized surface. Preferably, thepolishing surface is adapted for polishing a substrate selected from atleast one of a magnetic substrate, an optical substrate and asemiconductor substrate. More preferably, the polishing surface isadapted for polishing a semiconductor substrate.

To improve CMP polishing efficiency, the polishing layer of the CMPpolishing pads of the present invention are provided with bothmacrotextures, such as perforations or grooves, and microtextures as areformed by a conditioning disk, as disclosed in U.S. Pat. No. 5,489,233.

Preferably, the polishing surface has macrotexture selected from atleast one of perforations and grooves. Perforations can extend from thepolishing surface part way or all the way through the thickness of thepolishing layer. Preferably, grooves are arranged on the polishingsurface such that upon rotation of the chemical mechanical polishing padduring polishing, at least one groove sweeps over the surface of thesubstrate being polished. Preferably, the polishing surface hasmacrotexture including at least one groove selected from the groupconsisting of curved grooves, linear grooves and combinations thereof.

Preferably, polishing layer of the chemical mechanical polishing pad ofthe present invention has a polishing surface with a macrotexturecomprising a groove pattern formed therein. Preferably, the groovepattern comprises a plurality of grooves. More preferably, the groovepattern is selected from a groove design.

Preferably, the groove design is selected from the group consisting ofconcentric grooves (which may be circular or spiral), curved grooves,cross hatch grooves (e.g., arranged as an X-Y grid across the padsurface), other regular designs (e.g., hexagons, triangles), tire treadtype patterns, irregular designs (e.g., fractal patterns), andcombinations thereof. More preferably, the groove design is selectedfrom the group consisting of random grooves, concentric grooves, spiralgrooves, cross-hatched grooves, X-Y grid grooves, hexagonal grooves,triangular grooves, fractal grooves and combinations thereof. Mostpreferably, the polishing surface has a spiral groove pattern formedtherein. The groove profile is preferably selected from rectangular withstraight side walls or the groove cross section may be “V” shaped, “U”shaped, saw tooth, and combinations thereof.

The CMP polishing pads in accordance with the present invention may bemade by methods comprising: providing the isocyanate terminated urethaneprepolymer; providing separately the curative component; and, combiningthe isocyanate terminated urethane prepolymer and the curative componentto form a combination; allowing the combination to react to form aproduct; forming a polishing layer from the product, such as by skivingthe product to form a polishing layer of a desired thickness andgrooving the polishing layer, such as by machining it; and, forming thechemical mechanical polishing pad with the polishing layer.

The isocyanate terminated urethane prepolymer used in the formation ofthe polishing layer of the chemical mechanical polishing pad of thepresent invention preferably comprises: a reaction product ofingredients, comprising: a polyfunctional isocyanate and a prepolymerpolyol.

Preferably, the polyfunctional isocyanate is selected from the groupconsisting of an aliphatic polyfunctional isocyanate, an aromaticpolyfunctional isocyanate and a mixture thereof. More preferably, thepolyfunctional isocyanate is a diisocyanate selected from the groupconsisting of 2,4-toluene diisocyanate; 2,6-toluene diisocyanate;4,4′-diphenylmethane diisocyanate; naphthalene-1,5-diisocyanate,toluidine diisocyanate; para-phenylene diisocyanate; xylylenediisocyanate; isophorone diisocyanate; hexamethylene diisocyanate;4,4′-dicyclohexylmethane diisocyanate; cyclohexanediisocyanate; and,mixtures thereof.

Preferably, the prepolymer polyol is selected from the group consistingof diols, polyols, polyol diols, copolymers thereof, and mixturesthereof. More preferably, the prepolymer polyol is selected from thegroup consisting of polyether polyols (e.g.,poly(oxotetramethylene)glycol, poly(oxypropylene)glycol,poly(oxyethylene)glycol); polycarbonate polyols; polyester polyols;polycaprolactone polyols; mixtures thereof; and, mixtures thereof withone or more low molecular weight polyols selected from the groupconsisting of ethylene glycol; 1,2-propylene glycol; 1,3-propyleneglycol; 1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol;1,4-butanediol; neopentyl glycol; 1,5-pentanediol;3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropyleneglycol; and, tripropylene glycol. Still more preferably, the prepolymerpolyol is selected from the group consisting of at least one ofpolytetramethylene ether glycol (PTMEG); polypropylene ether glycols(PPG), and polyethylene ether glycols (PEG); optionally, mixed with atleast one low molecular weight polyol selected from the group consistingof ethylene glycol; 1,2-propylene glycol; 1,3-propylene glycol;1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol;1,4-butanediol; neopentyl glycol; 1,5-pentanediol;3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropyleneglycol; and, tripropylene glycol. Most preferably, the prepolymer polyolis primarily (i.e., 90 wt %) PTMEG.

Preferably, the isocyanate terminated urethane prepolymer has anunreacted isocyanate (NCO) concentration of 8.5 to 9.5 wt % (morepreferably, 8.75 to 9.5 wt %; still more preferably, 8.75 to 9.25; mostpreferably, 8.95 to 9.25 wt %). Examples of commercially availableisocyanate terminated urethane prepolymers include Imuthane® prepolymers(available from COIM USA, Inc., such as, PET-80A, PET-85A, PET-90A,PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene® prepolymers(available from Chemtura, such as, LF 800A, LF 900A, LF 910A, LF 930A,LF 931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667,LF 700D, LF750D, LF751D, LF752D, LF753D and L325); Andur® prepolymers(available from Anderson Development Company, such as, 70APLF, 80APLF,85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF).

Preferably, the isocyanate terminated urethane prepolymer is a low freeisocyanate terminated urethane prepolymer having less than 0.1 wt % freetoluene diisocyanate (TDI) monomer content.

The curative component used in the formation of the polishing layer ofthe CMP polishing pad of the present invention contains a polyolcurative and a polyfunctional aromatic amine curative, such as adifunctional curative.

Examples of commercially available polyol curatives include Specflex™polyols, Voranol™ polyols and Voralux™ polyols (available from The DowChemical Company). A number of preferred polyol curatives are listed inTable 1A, below.

TABLE 1A Polyols Number of Hydroxyl High molecular weight OH groupsNumber polyol curative per molecule M_(N) (mg KOH/g) VORANOL ™ 5055HPolyol 6.0 11,400 30 VORANOL ™ 4053 Polyol 6.9 12,420 31 VORALUX ™ HF505 6.0 11,400 30

Preferably, the difunctional curative is selected from diols anddiamines. More preferably, the difunctional curative used is a diamineselected from the group consisting of primary amines and secondaryamines. Still more preferably, the difunctional curative used isselected from the group consisting of diethyltoluenediamine (DETDA);3,5-dimethylthio-2,4-toluenediamine and isomers thereof;3,5-diethyltoluene-2,4-diamine and isomers thereof (e.g.,3,5-diethyltoluene-2,6-diamine);4,4′-bis-(sec-butylamino)-diphenylmethane;1,4-bis-(sec-butylamino)-benzene; 4,4′-methylene-bis-(2-chloroaniline);4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA);polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenylmethane; p,p′-methylene dianiline (MDA); m-phenylenediamine (MPDA);4,4′-methylene-bis-(2-chloroaniline) (MBOCA);4,4′-methylene-bis-(2,6-diethylaniline) (MDEA);4,4′-methylene-bis-(2,3-dichloroaniline) (MDCA);4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane,2,2′,3,3′-tetrachloro diamino diphenylmethane; trimethylene glycoldi-p-aminobenzoate; and mixtures thereof. Most preferably, the diaminecuring agent used is selected from the group consisting of4,4′-methylene-bis-(2-chloroaniline) (MbOCA);4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA), and, isomersthereof.

Preferably, the sum of the active hydrogen groups reactive hydrogengroups (i.e., the sum of the amine (NH₂) groups and the hydroxyl (OH)groups) contained in the curative component (i.e., the high molecularweight polyol curative and the difunctional curative) divided by theunreacted isocyanate (NCO) groups in the isocyanate terminated urethaneprepolymer (i.e., the stoichiometric ratio) used in the formation of thepolishing layer of the CMP polishing pad of the present invention ispreferably 0.85:1 to 1.15:1 (more preferably 1.02:1 to 1.08:1; mostpreferably 1.04:1 to 1.06:1).

The polishing layer of the chemical mechanical polishing pad of thepresent invention may further comprises a plurality of microelements.Preferably, the plurality of microelements are uniformly dispersedthroughout the polishing layer. Preferably, the plurality ofmicroelements is selected from entrapped gas bubbles, hollow corepolymeric materials, liquid filled hollow core polymeric materials,water soluble materials and an insoluble phase material (e.g., mineraloil). More preferably, the plurality of microelements is selected fromentrapped gas bubbles and hollow core polymeric materials uniformlydistributed throughout the polishing layer. Preferably, the plurality ofmicroelements has a weight average diameter of less than 150 μm (morepreferably of less than 50 μm; most preferably of 10 to 50 μm).Preferably, the plurality of microelements comprise polymericmicroballoons with shell walls of either polyacrylonitrile or apolyacrylonitrile copolymer (e.g., Expancel® microspheres from AkzoNobel). Preferably, the plurality of microelements are incorporated intothe polishing layer at 0 to 50 vol. % porosity (preferably 10 to 35 vol.% porosity). The vol. % of porosity is determined by dividing thedifference between the specific gravity of an unfilled polishing layerand specific gravity of the microelement containing polishing layer bythe specific gravity of the unfilled polishing layer.

The polishing layer of the CMP polishing pad of the present inventioncan be provided in both porous and nonporous (i.e., unfilled)configurations. Preferably, the polishing layer of the chemicalmechanical polishing pad of the present invention exhibits a density of≥0.4 g/cm³ as measured according to ASTM D1622-14 (2014). Preferably,the polishing layer of the chemical mechanical polishing pad of thepresent invention exhibits a density of 0.4 to 1.15 g/cm³ (morepreferably, 0.70 to 1.0; as measured according to ASTM D1622 (2014)).

Preferably, the polishing layer of the chemical mechanical polishing padof the present invention exhibits a Shore D hardness of 28 to 64 asmeasured according to ASTM D2240 (2015). More preferably, the polishinglayer of the chemical mechanical polishing pad of the present inventionexhibits a Shore D hardness of 30 to 60 (most preferably 35 to 55) asmeasured according to ASTM D2240 (2015).

Softer polishing layer materials tend to polish substrates at a lowerrate than harder polishing layer materials. Notwithstanding, softerpolishing layer materials tend to create fewer polishing defects thanharder polishing layer materials. The unique curative component used inthe formation of the polishing layer of the CMP polishing pad of thepresent invention provides reduced dishing without lowering removalrate.

Preferably, the polishing layer has an average thickness of 20 to 150mils. More preferably, the polishing layer has an average thickness of30 to 125 mils (still more preferably 40 to 120 mils; most preferably 50to 100 mils).

Preferably, the CMP polishing pad of the present invention is adapted tobe interfaced with a platen of a polishing machine. Preferably, the CMPpolishing pad is adapted to be affixed to the platen of a polishingmachine. Preferably, the CMP polishing pad can be affixed to the platenusing at least one of a pressure sensitive adhesive and vacuum.

The CMP polishing pad of the present invention optionally furthercomprises at least one additional layer interfaced with the polishinglayer. Preferably, the CMP polishing pad optionally further comprises acompressible base layer adhered to the polishing layer. The compressiblebase layer preferably improves conformance of the polishing layer to thesurface of the substrate being polished.

An important step in substrate polishing operations is determining anendpoint to the process. One popular in situ method for endpointdetection involves providing a polishing pad with a window, which istransparent to select wavelengths of light. During polishing, a lightbeam is directed through the window to the substrate surface, where itreflects and passes back through the window to a detector (e.g., aspectrophotometer). Based on the return signal, properties of thesubstrate surface (e.g., the thickness of films thereon) can bedetermined for endpoint detection purposes. To facilitate such lightbased endpoint methods, the chemical mechanical polishing pad of thepresent invention, optionally further comprises an endpoint detectionwindow. Preferably, the endpoint detection window is selected from anintegral window incorporated into the polishing layer; and, a plug inplace endpoint detection window block incorporated into the chemicalmechanical polishing pad. One of ordinary skill in the art will know toselect an appropriate material of construction for the endpointdetection window for use in the intended polishing process.

Preferably, the method of making a chemical mechanical polishing pad ofthe present invention, comprises: providing an isocyanate terminatedurethane prepolymer having 8.5 to 9.5 wt. % (preferably, 8.95 to 9.25wt. %) unreacted NCO groups; and, providing a curative componentcomprising: (i) from 60.3 to 70 wt. %, preferably, 60.5 to 67 wt. %, or,more preferably, 60.6 to 65 wt. %, based on the solids weight of thecurative component, of a polyol curative, having a number averagemolecular weight of 6000 to 15,000, or, preferably, from 10,000 to13,000 and an average of 5 to 7 or, preferably, 6 hydroxyl groups permolecule; and, (ii) providing from 30 to 39.7 wt. %, preferably, 33 to39.5 wt. %, or, more preferably, 35 to 39.4 wt. %, based on the solidsweight of the curative component, of a polyfunctional aromatic aminecurative, such as a difunctional amine curative;

combining the isocyanate terminated urethane prepolymer and the curativesystem to form a combination; allowing the combination to react to forma product; forming a polishing layer from the product; and, forming theCMP polishing pad with the polishing layer.

The methods of making a CMP polishing pad of the present invention mayfurther comprise: providing a plurality of microelements; and, whereinthe plurality of microelements is combined with the isocyanateterminated urethane prepolymer and the curative component to form thecombination.

The method of making a CMP polishing pad of the present invention,optionally, further comprises: providing a mold; pouring the combinationinto the mold; and, allowing the combination to react in the mold toform a cured cake; wherein the polishing layer is derived from the curedcake. Preferably, the cured cake is skived to derive multiple polishinglayers from a single cured cake. Optionally, the method furthercomprises heating the cured cake to facilitate the skiving operation.Preferably, the cured cake is heated using infrared heating lamps duringthe skiving operation in which the cured cake is skived into a pluralityof polishing layers.

The method of making the CMP polishing pad of the present invention,optionally, further comprises: providing at least one additional layer;and, interfacing the at least one additional layer with the polishinglayer to form the chemical mechanical polishing pad. Preferably, the atleast one additional layer is interfaced with the polishing layer byknown techniques, such as, by using an adhesive (e.g., a pressuresensitive adhesive, a hot melt adhesive, a contact adhesive).

The method of making the CMP polishing pad of the present invention,optionally, further comprises: providing an endpoint detection window;and, incorporating the endpoint detection window into the chemicalmechanical polishing pad.

The present invention will now be described in detail in the followingExamples.

EXAMPLES

Table 1 below summarizes compositions of a polishing layer of thepresent invention and a prior art example.

Prepolymer 1 comprises Adiprene™ L325 prepolymer having 8.95 to 9.25 wt.% unreacted NCO groups, made from toluene diisocyanate (TDI),polytetramethylene glycol (PTMEG), and 4,4′-methylene dicyclohexyldiisocyanate (H₁₂MDI) (Chemtura, Philadelphia, Pa.);

MbOCA is 4,4′-methylene-bis-(2-chloroaniline); and,

Voranol™ 5055 HH polyol (Dow) has an average of 6 hydroxyl groups permolecule and a number average molecular weight of 11,400.

TABLE 1 CMP Polishing Layer Compositions Curative Component Aromatic EX.amine curative Polyol Curative Molar ratio NO Prepolymer (% NCO) (wt. %)(wt. %) (Curative/NCO) 1C* 1 9.1 MbOCA 53.5 Voranol 46.5 1.05 5055HH 1 19.1 MbOCA 39.2 Voranol 60.8 1.05 5055HH *Denotes Comparative Example.

The formulations in Table 1 were cured at 104° C. for a period of 15.5hours to make a bulk cured polishing layer material. Unfilled bulkmaterials (38 mm by 38 mm squares of 2 mm thick) were soaked indeionized (DI) water for one week. Water uptake was calculated by thepercent weight change of each material. Pad hardness was measured beforeand after one week of water soaking, referred as dry and wet hardness,respectively. The wet hardness was measured on soaked samples aftersurface water had been removed. Sample hardness was recorded at both2-seconds (2s) and 15-seconds (15s). Table 2, below summarizes wateruptake and Shore D hardness measured before and after one week of watersoaking.

TABLE 2 Polishing Layer Properties Shore D Shore D Shore D Shore D HardWater Ex SG, hardness, hardness, hardness, hardness, segment uptake, No.unfilled 2 s dry 15 s dry 2 s, wet 15 s, wet content wt. % 1C* 1.15 61.758.8 54.7 49.2 42% 3.4 1 1.14 54.1 50.1 46.0 37.2 36% 5.0 *DenotesComparative Example.

The hard segment content was calculated from the percentage hard segmentin the polishing layer contributed mainly by the isocyanate component inthe isocyanate terminated urethane prepolymer and the polyfunctionalaromatic amine curative in the curative component. The balance wasconsidered the soft segment, comprising mainly the prepolymer polyolused in making the isocyanate terminated urethane prepolymer and thepolyol curative in the curative component.

To evaluate the polishing layers shown in Table 1, above, thepolyurethane materials were skived to a thickness of 2 mm (80 mil) thickand were grooved in a circumferential K7 pattern (concentric circulargroove pattern, with a groove pitch of 1.78 mm (70 mils), groove widthof 0.51 mm (20 mils) and groove depth of 0.76 mm (30 mils)) to form a775 mm (30.5 inch) diameter polishing layer; the polishing layer wasthen adhered to a SP2310™ sub-pad, commercially available from The DowChemical Company, Midland, Mich. The resulting CMP polishing pads wereused with a commercial bulk copper slurry (CSL9044C colloidal silicaabrasive particle slurry, Fujifilm Planar Solutions, Minato, Tokyo,Japan) at 300 ml/min to polish both copper sheet and pattern wafers.Polishing was conducted in an Applied Materials Reflexion™ LK 300 mmpolisher. The CMP polishing pad was broken in with a Kinik I-PDA31G-3Nconditioning disk (Taipei City, Taiwan, R.O.C.) at 2.27 kg (5 lbs) downforce for 30 mins with DI water, with the platen rotating at 93 rpm andthe conditioning disk rotating at 81 rpm. Following break in, the CMPpolishing pad was used to polish 20 pcs of tetraethoxysilane (TEOS)oxide dummy wafers, before performance data was collected on threecopper sheet wafers and one copper pattern wafer. Polishing the coppersheet and pattern wafers was performed with a polishing down force of1.135 kg (2.5 psi), with the platen rotating at 93 rpm, and thewafer/carrier rotating at 87 rpm. After polishing, the substrate wascleaned with CX-100 cleaning solution (Wako Pure Chemical Industries,Ltd, Osaka, Japan). After cleaning, defectivity and dishing performancewas determined.

Defectivity on Cu Sheet Wafers:

Defectivity was determined using Surfscan™ SP2 unpatterned wafer surfaceinspection tool (KLA-Tencor Corporation, Milpitas, Calif.) at athreshold 0.049 um. At 1.135 kg (2.5 psi) polishing down force, theaverage number of scratches in the polished copper sheet wafers areshown in Table 3, below.

TABLE 3 Polishing Defectivity Results Ex No. Average scratch/chattermark defect count 1C* 50.3 1 14.3 *Denotes Comparative Example.

The method of the present invention has demonstrated significantlyimproved defectivity performance than the methods of the ComparativeExample 1C.

Dishing on Pattern Wafer:

Dishing during the polishing of a pattern wafer was evaluated using anend-point-detection (EPD) system to detect the endpoint for copper (Cu)film clearing (the end point of polishing). The EPD system detects asignal change as different film materials are exposed by polishing. Anover-polish step was performed after the endpoint was detected to ensurethe Cu film was cleared except inside the oxide trenches of the patternwafer. The polish time of the over-polish step was set as a fixedpercentage of the previous EPD time to achieve a similar over-polishamount in different wafers or different pads. After polishing, a BrukerAFM Probes™ tool (Billerica, Mass.) was used to measure dishing andtopography at different feature sizes on the polished pattern wafer andto calculate total-indicated-range (TI R) using the tool's software. Thedishing performance from Cu pattern wafer polishing is shown in Table 4,at feature sizes of both 100×100 μm and 50×50 μm.

TABLE 4 Dishing Performance Dishing improvement Dishing improvement ExNo. at 100 × 100 μm at 50 × 50 μm 1C* Control Control C 18% 12% *DenotesComparative Example.

Table 4 shows substantial dishing improvement from the methods of thepresent invention when compared to the method of polishing using a CMPpolishing pad made using less of the polyol curative of the presentinvention in Comparative Example 1C. It was unexpected that methods ofpolishing with a softer pad from in accordance with the presentinvention provides similar or better dishing than the methods ofpolishing with a harder pad as in Comparative Example 1C.

1-10. (canceled)
 11. A CMP polishing pad useful for polishing a metalsurface on a semiconductor wafer, the CMP polishing pad comprising: apolishing layer, the polishing layer having a top polishing surface, theCMP polishing pad and polishing layer comprising: a cured reactionproduct of an isocyanate terminated urethane prepolymer, the isocyanateterminated urethane prepolymer being a blend of toluene diisocyanate,polytetramethylene glycol and 4,4′-methylene dicyclohexyl diisocyanatehaving 8.5 to 9.5 wt. % of unreacted NCO groups; and a curativecomponent consisting essentially of from 60.3 to 70 wt. %, based on thesolids weight of the curative component, of a polyol curative having anumber average molecular weight of 6,000 to 15,000 and having an averageof 5 to 7 hydroxyl groups per molecule; and from 30 to 39.7 wt. %, basedon the solids weight of the curative component, of 4,4′ methylene bis (2chloroaniline), wherein a cured unfilled formulation of the CMPpolishing pad and polishing layer lacking added porosity, has a wateruptake of 4 to 8 wt. % after one week of soaking in deionized (DI) waterat room temperature and a Shore D hardness ranging of from 28 to 64, thetop polishing surface being adapted for planarizing and polishing themetal surface of the semiconductor wafer.
 12. The CMP polishing pad asclaimed in claim 11, wherein the curative component of the polyolcomponent is 60.6 to 65 wt %, based on the solids weight of the curativecomponent.
 13. The CMP polishing pad as claimed in claim 11, wherein theCMP polishing pad has a Shore D hardness of from 30 to
 60. 14. The CMPpolishing pad as claimed in claim 11, wherein the CMP polishing has aShore D hardness of from 35 to
 55. 15. The CMP polishing pad as claimedin claim 11, wherein the CMP polishing pad comprises CMP polishingstoichiometric ratio of reactive hydrogen groups (defined as sum of NH₂and OH groups) in the curative component to the unreacted NCO groups inthe isocyanate terminated urethane prepolymer ranges from 0.85:1 to1.15:1.
 16. The CMP polishing pad as claimed in claim 11, wherein thecurative is substantially free of any diol.
 17. The CMP polishing pad asclaimed in claim 11, wherein the CMP polishing pad has a specificgravity (SG) of from 0.4 to 1.15 and the cured unfilled formulation ofthe CMP polishing pad and polishing layer lacking added porosity has anSG of from 1.1 to
 12. 18. The CMP polishing pad as claimed in claim 11,wherein the CMP polishing pad and polishing layer comprise gas filled orhollow microelements.